In recent years, devices, which handle image information as digital data, which, in such a case, aim to transmit and store information with a high efficiency, and which conform to a scheme, such as MPEG2 (International Organization for Standardization and International Electrotechnical Commission (ISO/IEC) 13818-2), for compressing image information using orthogonal transformation, such as discrete cosine transformation, and using motion compensation by utilizing redundancy that is unique to the image information have become widespread in both information distribution in broadcasting stations and information reception in ordinary homes. In addition, schemes called H.264 and MPEG4 Part10 (Advanced Video Coding (AVC) which require a larger amount of operation for coding and decoding but can realize a higher coding efficiency than MPEG2 or the like have been also used. Further, nowadays, standardization works for high efficiency video coding (HEVC) which is a next-generation image coding scheme are in progress so that compression, distribution, or the like of high-resolution images of 4000×2000 pixels which is four times that of high-vision images can be performed efficiently.
In the standardization works for high efficiency video coding (HEVC) which is a next-generation image coding scheme, JCTVC-A119 (see Non-Patent Document 1 below) proposes to apply a deblocking filter to each block having the size of 8×8 pixels or larger. In the method proposed in JCTVC-A119, by increasing a minimum unit block size to which a deblocking filter is to be applied, it is possible to execute a filtering process in parallel on a plurality of block boundaries in the same direction within one macroblock.